The present invention is directed to a trailer for the transport of loads, and more particularly, to an adjustable trailer in which the dimensions of the trailer may be adjusted to accommodate various equipment loads of different dimensions.
Significant governmental regulations exist which establish maximum height and width limits for trailers and other equipment and vehicles which are to be transported over public roads and highways. The older regulations in the United States establish the maximum legal width at 8 feet. Some of the more recent regulations have increased that maximum width, but even as so increased, the maximum legal width does not exceed 8.5 feet. Any vehicle or load exceeding the regulation maximum width is generally considered to be a wide load and, although it might be transportable, is subject to a number of restrictions. Moreover, if a trailer for transporting such wide loads, even if it is capable of enlargement in width to accommodate the additional load width, the enlarged width trailer is only permitted on the highways with the wide load on it. Once the load has been offloaded from the trailer, most regulations require that the width of the trailer must be within the maximum regulation width if the trailer is to be transported in an empty condition on the highway. Thus, in order to be practical, trailers capable of transporting loads of wide widths which exceed regulations must typically be somehow adjustable to permit return to the regulation width when empty so that they are capable of highway transport when empty or no restrictions when they are transporting loads of regulation widths. Maximum height restrictions also exist and these are typically 13.5 feet, or more recently 14 feet to permit clearance of bridges and other overhead obstructions.
In order to accommodate loads of widths and heights which meet legal restrictions, as well as loads which may have width dimensions which exceed such restrictions, and/or heights which when loaded on a trailer might exceed total height restrictions, various approaches have been taken in trailer construction for the support and transport of such large dimension loads. As to loads which have height dimensions which approach the maximum height restrictions when loaded on the trailer, a class of trailer has evolved which is generally referred to as a "lowboy" trailer. In such lowboy trailers at least a portion of the trailer deck is constructed to be as close to the roadway as possible. This permits the transport of loads which are of greater height and which might be close to the maximum height restrictions. With respect to load widths, lowboy and other trailers have also been constructed to permit the adjustment of their width so that they can be adjusted to either a minimum width configuration in which they are capable of supporting and transporting loads or equipment which are within governmental width restrictions, a maximum width configuration in which wide loads which exceed width restrictions may be supported and transported, and reduced back to minimum width when empty so that they may be transported empty on highways. An example of the latter maximum width loads may include some combine equipment in which the tread width of the combine may be of greater width than the governmental width restrictions.
One prior trailer width adjustment has typically been effected in the past by the provision of pullout platforms which are capable of being moved transversely and horizontally of the deck from beneath the deck surface in a drawer-like fashion to effectively increase the width of the deck surface when pulled out. However, such pullout platform constructions suffer several disadvantages. One disadvantage is that if any portion of the pullout platform becomes bent or sprung in any manner, movement of the platform either in or out is substantially impaired if not precluded altogether until the bend is fixed. Moreover, such pullout constructions are not as strong as the construction of the main deck itself. This itself can lead to the bending or distortion of the platforms when pulled out and loaded with heavy equipment which will tend to bounce on the platform during transport. If the platform structural strength is to be maximized to minimize such bending or distortion in use, its weight generally must be substantially increased. This can result in a loss of fuel economy and ability to meet pertinent weight regulations, and require hydraulic or other power systems for operation, rather than simple, less complex and inexpensive manual operation. Another disadvantage of the prior pullout platform constructions is that even when pulled out, there will be no appreciable change in deck height. Thus, no advantage is realized in the way of reduction of overall height of the load which may be important to meet some height regulations.
Another prior trailer width adjustment construction has included a drop leaf arrangement in which a plate is hinged for rotation to the upper edge of the trailer deck. When in the minimum width position, the plate hangs down much like a table drop leaf. When it is moved to the maximum width position, it is swung upward 90.degree. to extend from the deck to form a continuation extension of the main deck of the trailer, much like a table drop leaf. The plate is supported in the up, maximum width position either by pullout supports as last described or by swing out supports which swing out about a vertical axis beneath the plate. The pullout support constructions suffer the same disadvantages as the pullout extensions previously described. Moreover, both support mechanisms lack strength and, therefore, are subject to bending and springing and a reduction in the load weight that can be supported. The amount of width enlargement that is possible in these drop leaf constructions is also substantially limited, particularly in lowboy trailers, due to the already low positioning of the trailer deck to the roadway which restricts the amount of plate width that can hang down in the minimum width position. Furthermore, there is no height adjustment in these drop leaf arrangements.
In a variation of the last mentioned drop leaf arrangements, the hinged drop leaf also has been replaced in part by simply placing planking on either the pullout or swing out supports to extend the width of the trailer deck. Although this arrangement may permit greater width enlargement than the drop leaf construction, it suffers all of the other disadvantages of such constructions. In addition, the supports tend to move relative to the relatively loose planking or vice versa during transport, and this increases the possibility of collapse in use and/or loss of the planking in or between uses.